Simplify hotkey event generation by using a sparse keymap.  As sparse
keymap operates on scancodes instead of keycodes, adjust variable names
and debug messages accordingly.

This patch only handles the default keymap for clarity.
Signed-off-by: NMichał Kępień <kernel@kempniu.pl>
Reviewed-by: NJonathan Woithe <jwoithe@just42.net>
[dvhart: correct flag passed to call_fext_func in acpi_fujitsu_laptop_notify]
Signed-off-by: NDarren Hart (VMware) <dvhart@infradead.org>